altcoin rate of change is much faster than bitcoin because higher price and volume is smaller compared to other cryptocoin
Exactly, the more lower volume the easier those whales could control its price, for example an altcoin that having 24 hours volume with only 10 bitcoin
when a whale suddenly came and pumping it with only 5 bitcoin which is half of the current 24 hours volume then the price could probably increasing about 100% or even more. And altcoin sometimes could lost its trust by their holders so it's more volatile compared to bitcoin
Pumping doesn't work this way
If an altcoin has a trading volume of only 10 bitcoins daily (or something to that tune), it is essentially dead, and if some whale decides to pump this altcoin, he will only lose his money since there would certainly be a lot of people ready to cash out and forget about this coin for good. Pumping with subsequent dumping is used obviously for earning profits, and it is assumed that after the initial pump the price will continue to rise, at least for some time (so-called fear of missing out or panic buying), so that the dumping part would be profitable ("buy low, sell high")